ABSTRACT Nine Investigators from the RR&D Center for Limb Loss Prevention and Prosthetic Engineering are requesting funds to acquire a new biplane fluoroscopy system. This system will support a variety of projects that are working towards the Center's core mission of improving the quality of life and functional status of both veterans who are at risk for lower extremity amputation, and veterans and service members who have undergone lower extremity amputation. The biplane fluoroscopy system consists of a pair of fluoroscope components mounted to a number of free-standing adjustment gantries. Each fluoroscope is comprised of an X-ray generator, which produces and emits X-ray radiation, and an image intensifier (II) which collects the X-rays and converts them to visible light. Mounted behind each II is a high-speed video camera, which captures the visible-light images appearing on the II at a high acquisition rate (up to 1000 frames/sec). The X-ray generator and II's are mounted to a floor-mounted stand which provides for motor-driven vertical adjustment of the position of the X- rays and II's. A system interface synchronizes the X-ray acquisition with the video cameras, and provides triggering capabilities with external hardware. The requested biplane fluoroscopy system is a major upgrade to our current system which was purchased in 2007-08 and uses outdated technology. As noted above, there are three major components to the biplane system: 1) the X-ray generators and IIs, 2) the support stands or gantries, and 3) the high speed video cameras. Each of these subsystems will be replaced. The biplane fluoroscopy system will support a number of projects that span the Center's research portfolio: Quantitative Prescription of Foot Orthoses: A Dose-Response Study of Kinematics in Patients with Foot and Ankle Pain using Biplane Fluoroscopy. A biplane fluoroscopy assessment of the dose response of foot kinematics to varying degrees of hindfoot posting will be conducted. Do Rocker Bottom Shoes and Ankle-Foot Orthoses Reduce Pain and Improve Mobility for Ankle Osteoarthritis Patients? A biplane fluoroscopy assessment of foot kinematics in response to rocker bottom shoes and ankle-foot orthoses will be conducted. Residual Limb Skeletal Movement During gait. A biplane fluoroscopy assessment of residual limb bone kinematics will be conducted. The Biomechanics of Lateral Wedge Insoles. A biplane fluoroscopy assessment of foot kinematics in response to lateral wedge insoles will be conducted. Reducing Internal Stresses in Deformed Diabetic Feet. A biplane fluoroscopy assessment of foot kinematics will provide high resolution images of foot and ankle bone motion for model validation. Improving the Detection, Classification and Treatment of Misaligned Arthritic Ankles. A biplane fluoroscopy assessment of foot kinematics of ankle osteoarthtitis subjects will be conducted. Mapping The Soft Tissue Artifact of the Foot and Ankle and Evaluating Site Specific Errors based on Subject Characteristics. The biplane system will be used to determine soft tissue artifact at optical marker locations, in order to build error-mapping databases. Comparing Surgical Treatments for Hallux Rigidus Using a Biomechanically and Anatomically Realistic Foot Model. The biplane system will be used to collect validation data on patients that were used to generate HR models.